Washcoat and Active Material

The yield of acetaldehyde, which is the major by-product formed, as well as the yield of acetic acid, are strongly influenced by the choice of both support and active material. The metal-support interaction also has a certain influence on the oxidation of nitric oxide to nitrogen dioxide. It has been demonstrated that the propensity for the catalyst to produce nitrogen dioxide at elevated temperatures can be selectively inhibited by the combination of appropriate washcoat and active materials. 

In this section, recent development of high temperature stable support materials as well as washcoat and active materials is reviewed. Some of the most promising materials to be used as supports in catalytic combustion for gas turbine applications are summarized in Table 1. These monolithic support materials, such as alumina or zirconia, could also be used as washcoat materials with another preparation method. Typical light-off temperatures and specific surface areas for some of the interesting catalyst compositions are summarized in Table 2. 

As a preventive solution to the problem of NOx emissions, catalytic combustion has come to the forefront during the last two decades. The focus of major interest here is its application in gas turbines for power generation and for transportation by road, water or air. Any catalyst for catalytic combustion, however, has to face extreme demands above 1000°C in the presence of oxygen and steam, in uninterrupted operation for at least one year also, resistance to impurities or poisons in the fuel and to severe thermal and mechanical shocks. Promising developments in catalytic supports, washcoats and active materials are reviewed briefly. 

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